Rebuilding the crop-livestock integration system in China ——Based on the perspective of circular economy

From the perspective of the agricultural circular economy, rebuilding the crop-livestock integration system contributes a lot to improving the recycling rate of livestock manure, and reducing the application of synthetic chemical fertilizers, thereby fundamentally curbing agricultural pollution. In this paper, we use the latest provincial statistical data of China (2000–2020) to assess the circulation linkage between crop and livestock production. It can be concluded that livestock manure nitrogen and nitrogen requirements of crops both show an increasing trend from 2000 to 2020. Cropland Carrying Capacity of Breeding Livestock (CCCBL) has risen significantly by 37.34%, with an increase of 0.97 × 109 heads (unit: pig equivalent, which is used to measure livestock manure emission). Cropland Carrying Capacity Index (CCCI) exhibits a decreasing trend with the index being 0.47 in 2020, which further indicates that China's cropland has a great potential for carrying more livestock manure. Furthermore, through the scenario simulation, it can be projected that the livestock manure nitrogen will be 18.91 Tg and nitrogen requirements of crops will be 36.14 Tg in 2050. Thereby, rebuilding the crop-livestock integration system is necessary to achieve the dual goal of economic development and environmental conservation. Finally, this paper proposes that the government should optimize the crop-livestock geographical distribution and promote the upgradation of circular agriculture.